Frank is the younger son of Henry (
Len Cariou) and Betty Reagan, born in
Bay Ridge, Brooklyn, New York in the early 1950s. His older brother, Peter Christopher Reagan, died of leukemia at the age of 18 months, over a year before Frank was born. Frank married Mary Margaret Reagan (née Conor) in the early 1970s, and they have four children together: Danny, Erin, Joe, and Jamie. Each of Frank's sons followed him into the NYPD: Danny (
Donnie Wahlberg) is a Detective 1st Grade and lead investigator with the 54th Precinct's Detective Squad; Joe was a Detective with the Warrants Squad who was murdered on the orders of his partner Sonny Malevsky (
Michael T. Weiss), the leader of a corrupt gang of police officers called the Blue Templar; and Jamie (
Will Estes), who received a law degree from
Harvard University before joining the force, first as a patrol officer, then as a Sergeant assigned to the 29th Precinct, and later as the Intelligence Officer for the 2-9 as of Season 13, Episode 2. Frank's only daughter, Erin (
Bridget Moynahan), is a
Manhattan Assistant District Attorney. Erin was promoted to Deputy Bureau Chief of the NYCDA's Trial Bureau in 2013. In addition to his children, Frank is also a loving grandfather to Erin's daughter, Nicky Reagan-Boyle (
Sami Gayle), and Danny's two children, Jack (Tony Terraciano) and Sean Reagan (Andrew Terraciano). It's revealed in Season 10's "Family Secrets" that Frank also has one more grandson, Joseph Hill, the son of Paula Hill, whom Joe Reagan met at the academy. Paula said the two had a brief affair and she never told Joe about her pregnancy or his son. Paula visits Frank and reveals the news in an effort to get her son, a young detective in the firearms unit, assigned to a less dangerous precinct. Soon Joe's connection to the family made public and he leaves for a while but after a dangerous undercover assignment, he returns to his family and comes to accept them, as well as his heritage. In one episode, it is mentioned that Frank's wife's grandfather was one of the builders on the
Brooklyn Bridge in the 1870s and '80s. Frank's dad's father, Charles Reagan, was an Irish immigrant who served in
World War I before becoming a police officer. Charles was the one who taught him how to fish. In "
Whistle Blower" (season 2, episode 10), Frank mentions his great-uncle Teddy Reagan, a member of the NYPD Mounted Unit, who spent a cold night in a boxcar with his horse, Dolly, and a flask, waking up much later in Pittsburgh. Growing up, Frank became friends with Angelo Gallo (
Chazz Palminteri), who grew up to be one of the top mafia lawyers. After Gallo was shot on the orders of a former client, Frank has him publicly arrested for hindering prosecution, to protect him from being considered a
rat. His other close friends include
Monsignor Walter Donahue, a member of the
city archdiocese, and Kevin Kearns (
Stacy Keach), the Archbishop of New York. However, it is also mentioned that Frank does not have many friends in the
New York City Council, especially after Danny's arrest of city Councilman Tony Mancini (
Richard Burgi), a former NYPD detective, for domestic abuse. ==Service==